Week 11 - Project - A pillar Design with Master Section

AIM

Create the A Pillar Plastic component through the given Class-A surface and master section and perform Draft analysis.

THEORY

CLASS A SURFACE: Class A surface is a surface made by the designer specially in automotive design which is the aesthetic part of a body and is given as an input to the plastic designer to work on it.

CLASS B SURFACE: It is a surface which comes below the class A surface with a particular thickness. This surface contains engineering features of a model.

CLASS C SURFACE: It is the surface which joins class A with class B surface.

A PILLAR: A-Pillars straddle the windshield, B-Pillars are in the middle of the passenger compartment (just behind the front doors) and C-Pillars are those at the rear of the passenger compartment.

MASTER SECTION: Master sections are the guides for design requirements which decide the component packaging after technical (Styling, Concept or Class-A) surfaces. Creating this master section should need 5 to 6 years of experience. This helps you to decide the feasibility, clearance, the packaging and the fixation strategy before working it on a 3D.

TOOLING AXIS: Tooling axis is the direction in which the core and cavity opens. If we are using proper tooling axis, we can avoid adding side cores thus the cost of manufacturing the component can be reduced.

It is defined as the direction in which the mould/core and cavity open. Selection of the direction of the tooling axis depends on the ease at which components can be easily ejected.

Generally tooling axis is decided from the natural axis of the design, that is, tooling axis is analysed with the x, y and z axis of the system. If the axis doesn’t clear the draft analysis, the next step is to look for the surface in which the drafting axis can be created in such a way that the axis is normal to the surface taken. These are the methods of deciding tooling axis. Bisecting method is the least used method.

BISECTING METHOD: It is a method used to create tooling axis. The sides of the surfaces are chosen in such a way that the edges may affect the tooling axis are taken as the input for the creation of tooling axis. This axis is then created by giving the line type as bisecting line and the inputs as the lines constructed from the edges that affects the tooling axis. This is not frequently used technique for creating tooling axis.

Here, tooling axis is created using the reference from the master section. As there is a doghouse present in the B side, the sides of the doghouse is taken to create the tooling axis. Two lines are drawn from the edges of doghouse and another line is drawn by using the line option as bisecting line, with inputs as these lines. Thus, the line obtained after these inputs is the tooling axis obtained from bisecting method.

DOG HOUSE: It is an engineering feature used in plastic trim design. It is used as a supporting feature. By using dog house, we can support the other engineering features like heat stakes, screw boss and locators to locate them at a certain height where we cannot violate the design rules for the features. By using doghouse, we can avoid sink marks in class A surface.

Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).

The height of ( B ) should be between 3.0 – 6.0 mm

DRAFT ANALYSIS: From draft analysis, we can verify draft angles, examine the angle changes within a face, as well as locate parting lines, injection and ejection surfaces in parts.

It is an important feature in Catia which helps the user to analyse the draft on various surfaces. The draft analysis toolbar provides two modes for analysis of the draft, first is the quick analysis which basically has three colours (green, red, and blue) for analysing on the other hand other option is the full analysis mode which enables a few more details into the draft and is used in the complex components.

OBJECTIVES

• Creation of Tooling axis
• Creation of Class B and Class C surface from provided Class A surface.
• Creation of solid part out of surface modelling.
• Create engineering features from the master section.
• Draft analysis of Class A surface and final part.

PROCEDURE

Creation Of Class A Surface

• Class A surface is obtained as the input.
• Join all the surfaces to obtain Class A surface if different surfaces are given as input and ensure no gap is present between any surfaces. Thus, Class A surface is obtained and publish it. Here, the provided surface is completely joined and can be taken as class A surface.
• Publish class A surface.

Creation Of Tooling Axis

• Tooling axis is created by bisecting method.
• Publish Tooling axis.

Draft Analysis Of Class A surface

• Draft analysis is performed over Class A surface and every surface is obtained as clearing.

Most of the surfaces obtained are green in color, which means that the surfaces are clearing the draft analysis.

Some faces of the surface are not clearing the draft. It is seen that the draft over those surfaces are having draft less than the nominal draft value of 3-degree. So, it is recommended for the class A designer to redesign the class A surface for obtaining all the surfaces cleared.

Creation Of Class B Surface

• Now, Class B surface has to be created. For this surface should be offsetted for 2.5mm.
• Publish class B surface.

From the master section, it is clear that the thickness to be provided for the plastic component is 2.5mm.

So, class B is offsetted for 2.5mm.

Creation Of Class C Surface

• Now class C surface has to be created and it is created from the boundaries obtained from the Class A surface. This boundary is provided as the input curve for sweep command. Using sweep command, class C surface is created.
• Appropriate sweep is the provided considering the flash and considering manufacturing procedures. Surfaces are extrapolated if necessary.
• Publish class C surface.

Creation Of Closed Surface

• Now Class A surface and Class C surface is joined.
• Now Class B surface is also trimmed with the obtained surface to get the closed surface.
• Boundary check is done to check for any open boundaries in the part.
• The closed surface then obtained moved to part design and close surface tool is used to obtain the part.

Draft Analysis Of Plastic Component

• The obtained part is draft analysed to check for the correctness of obtained model by following the draft analysis procedure mentioned above.

Class A Surfaces obtained are all green in color, which means that the surfaces are clearing the draft analysis. The faces that are obtained in red will be clearing in core side, as the draft direction is reversed, those red faces will be turned to green which means those surfaces are also clearing draft analysis.

Creation Of Doghouse

• Doghouse are created by following the design rules.
• For this, sketch is created from the master section provided.
• It is then made to closed body and is made to part model.
• Shell operation is performed to get hollow structure and then coring is done in order to avoid sink marks in the class A surface.
• Drafts are given for the surfaces as per design rules and proper fillets are also provided.
• As per the given master section, ribs and supporting features are also added in the doghouse.
• Then, the doghouse is added to the main body.

All the sketches used are iso-constraint.

Draft Analysis Of Plastic Component

• The obtained part is draft analysed to check for the correctness of obtained model by following the draft analysis procedure mentioned above.

Side core has to be created for the doghouse to get ejected. So, a side core axis is also created for checking the draft analysis of the component.

Minimum of 0.5-degree draft is provided and the B side engineering features are analysed using the side core axis. Green colour is obtained in the draft analysis, which indicates that the draft provided all are in correct direction.

Picture of the Detailed tree structure:

CONCLUSION

• Created Tooling axis
• Created Class B and Class C surface from provided Class A surface.
• Created solid part out of surface modelling.
• Created engineering features from the master section provided.
• Draft analysis of Class A surface and final part is also done.

REMARK: I'm using the latest version of CATIA. The file has been reviewed by the Technical Support Engineer.